As the components required to build a computer system have reduced in size, new categories of computer systems have emerged. One of the more recent categories of computer systems is the portable or “palmtop” computer system, or personal digital assistant (PDA). A palmtop computer system is a computer that is small enough to be held in the hand of a user and is thus “palm-sized.” As a result, palmtops are readily carried about in a briefcase or purse, and some palmtops are compact enough to fit into a person's pocket. By virtue of their size, palmtop computer systems are also lightweight and so are exceptionally portable and convenient.
Further development of PDAs has enabled their use for more and more tasks. For example, portable, and even wireless, access to computer networks is now readily available with suitably configured devices. The portability and convenience of palmtop devices has enabled the even more exciting possibilities encompassed by the combination of the capabilities of palmtop devices with the communication convenience of wireless phones, e.g. cellular phones.
As the capabilities of the two device types combine, and even combine into the same unit, new demands are made of the small display area available on these characteristically small devices. The display area of these portable devices is necessarily limited by the size of the devices themselves, which is their primary advantage. As the breadth of applications of portable devices increases, the display “real estate” of the devices becomes more and more used up. Each new application requires some new user interface. In particular, the use of a palmtop computing device that is also a cellular phone has been limited by interruptions of computing functions by incoming calls or by the need to leave the device in standby mode in order to receive calls.
What is required, therefore, is a means by which the palmtop device and/or wireless telephone can continue to be operated as a computing device yet still allow a user to receive and/or reject calls. The need further exists to allow call screening during continued computational use, without interruption of any applications in operation, by the sharing of the graphic display area.